The present invention relates generally to the cooling of jet engine components having surfaces exposed to the flow of high temperature gas. More particularly, in one embodiment the present invention defines a turbine vane or blade having internal passageways and exit holes for the passage of cooling media necessary for cooling the component. Although the present invention was developed for use in a gas turbine engine, certain applications may be outside of this field.
A gas turbine engine is typical of turbomachinery in which the concept described herein may be advantageously employed. It is well known that a gas turbine engine conventionally comprises a compressor for compressing air to the proper pressure required for supporting the combustion of fuel in a combustion chamber. The high temperature gas exiting the combustion chamber provides the working fluid for the turbine, which powers the compressor. The turbine, which is driven by the flow of high temperature gas, is utilized to turn a propeller, fan or other device. Further, the high temperature gas may be used directly as a thrust for providing motive power, such as in a turbine jet engine.
It is well known that the performance of a gas turbine engine increases with the increase in the operating temperature of the high temperature gas exiting the combustion chamber. A factor limiting the allowable temperature of the gaseous working flow from the combustion chamber is the capability of the various engine components to not degrade when exposed to the high temperature gas flow. Various techniques have been utilized by engine designers to cool the engine components in order to increase the upper limit on the operating temperature of the gaseous working fluid.
A conventional technique, film cooling has been widely utilized to minimize the degradation of the gas turbine engine components exposed to the flow of high temperature gases. Film cooling generally refers to a technique of cooling an external surface of the component that is being heated by the high temperature gas, and involves injecting a relatively cool media, such as air along the component's external surface. The cooling media functions as an insulating layer to reduce the unwanted heating of the external surface of the component by the flow of high temperature gas. A second conventional technique that engine designers have used to allow the use of higher temperature working gases is an internal network of apertures and passageways within the component. A steady flow of pressurized cooling media is passed through the internal passageways of the component, and the cooling media is finally exhausted onto the exterior surface of the component. The passage of the cooling media through the internal passageways and out through the exit aperture provides for convective heat transfer from the walls of the component to the cooling media.
Cooling of the components of the gas turbine engine is preferably accomplished with a minimum amount of cooling media, since the cooling media is working fluid, which has been extracted from the compressor, and its loss from the gas flow rapidly reduces engine efficiency. The engine designer must design an engine to operate within a specified temperature range, while minimizing the amount of cooling media extracted from the compressor. If these design parameters are not satisfied, a corresponding structural degradation of the engine components may result, or the efficiency of the engine may be reduced because an excessive quantity of cooling media was extracted from the compressor.
Although the prior techniques utilizing internal passageways, exit apertures, and film cooling are steps in the right direction for cooling components exposed to high temperature gases, the need for additional improvement still remains. The present invention satisfies this need in a novel and unobvious way.